serial: qcom-geni: Enable PM runtime for serial driver

The GENI serial driver currently handles power resource management
through calls to the statically defined geni_serial_resources_on() and
geni_serial_resources_off() functions. This approach reduces modularity
and limits support for platforms with diverse power management
mechanisms, including resource managed by firmware.

Improve modularity and enable better integration with platform-specific
power management, introduce support for runtime PM. Use
pm_runtime_resume_and_get() and pm_runtime_put_sync() within the
qcom_geni_serial_pm() callback to control resource power state
transitions based on UART power state changes.

Signed-off-by: Praveen Talari <praveen.talari@oss.qualcomm.com>
Link: https://patch.msgid.link/20251110101043.2108414-4-praveen.talari@oss.qualcomm.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: ptalari27

drivers/tty/serial/qcom_geni_serial.c

@@ -1650,10 +1650,10 @@ static void qcom_geni_serial_pm(struct uart_port *uport,
 		old_state = UART_PM_STATE_OFF;
 
 	if (new_state == UART_PM_STATE_ON && old_state == UART_PM_STATE_OFF)
-		geni_serial_resources_on(uport);
+		pm_runtime_resume_and_get(uport->dev);
 	else if (new_state == UART_PM_STATE_OFF &&
 		 old_state == UART_PM_STATE_ON)
-		geni_serial_resources_off(uport);
+		pm_runtime_put_sync(uport->dev);
 
 }
 
@@ -1815,6 +1815,8 @@ static int qcom_geni_serial_probe(struct platform_device *pdev)
 	if (ret)
 		return ret;
 
+	devm_pm_runtime_enable(port->se.dev);
+
 	ret = uart_add_one_port(drv, uport);
 	if (ret)
 		return ret;
@@ -1846,6 +1848,22 @@ static void qcom_geni_serial_remove(struct platform_device *pdev)
 	uart_remove_one_port(drv, &port->uport);
 }
 
+static int __maybe_unused qcom_geni_serial_runtime_suspend(struct device *dev)
+{
+	struct qcom_geni_serial_port *port = dev_get_drvdata(dev);
+	struct uart_port *uport = &port->uport;
+
+	return geni_serial_resources_off(uport);
+}
+
+static int __maybe_unused qcom_geni_serial_runtime_resume(struct device *dev)
+{
+	struct qcom_geni_serial_port *port = dev_get_drvdata(dev);
+	struct uart_port *uport = &port->uport;
+
+	return geni_serial_resources_on(uport);
+}
+
 static int qcom_geni_serial_suspend(struct device *dev)
 {
 	struct qcom_geni_serial_port *port = dev_get_drvdata(dev);
@@ -1889,6 +1907,8 @@ static const struct qcom_geni_device_data qcom_geni_uart_data = {
 };
 
 static const struct dev_pm_ops qcom_geni_serial_pm_ops = {
+	SET_RUNTIME_PM_OPS(qcom_geni_serial_runtime_suspend,
+			   qcom_geni_serial_runtime_resume, NULL)
 	SYSTEM_SLEEP_PM_OPS(qcom_geni_serial_suspend, qcom_geni_serial_resume)
 };